(12a) Accounting for Safety System Activation within Economic Model Predictive Control
AIChE Annual Meeting
Sunday, October 29, 2017 - 3:30pm to 3:49pm
Motivated by the above considerations, we develop an EMPC design that accounts for the activation conditions of the safety system and changes the process model when the safety system is predicted to be activated at any time throughout the prediction horizon to reflect the dynamics of the process after safety system activation. We consider modeling of the automated actions of both the emergency shutdown system and the safety relief system within the EMPC. We investigate the impact that the foreknowledge of the safety system activation has on the state and input trajectories of a chemical process under such a control design compared to the case that the EMPC is unaware of the safety system activation. We discuss the impact of the plant-model mismatch that may occur due to disturbances if the state predictions utilized for choosing the control actions indicate activation of the safety system but it does not activate for the process with disturbances (similarly, we discuss the impact of the safety system activating when it was not predicted within the EMPC to do so). We investigate the addition of constraints to the EMPC as the state predictions approach the safety system activation levels to encourage it to choose control actions that will prevent the safety system activation. The closed-loop modeling strategy developed that includes the safety system activation conditions may also provide a systematic methodology for identifying safety system triggers and thus for coordinating the control and safety systems.
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